1. Field of the Invention
The present invention relates to an eccentric oscillating gear mechanism for use in a joint portion of an industrial robot.
2. Related Art
There have conventionally been known eccentric oscillating gear mechanisms such as those used in joint portions of industrial robots (hereinafter, also referred to simply as a “robot” from time to time) which are described in JP-A-9-57678 and JP-A-2001-323972 below.
Eccentric oscillating gear mechanisms described in JP-A-9-57678 and JP-A-2001-323972 are an eccentric oscillating gear mechanism which includes an internal gear, an external gear which meshes with the internal gear, a crankshaft which moves the external gear eccentrically, and a carrier which supports the crankshaft rotatably. The internal gear and the carrier are made to rotate relatively. The eccentric oscillating gear mechanism includes a hollow hole which is made axially about an axis thereof, and a cylindrical tube body is made to penetrate the hollow hole. Then, wiring, tubing and cables are passed through a hollow hole made in the cylindrical tube body, whereby the cables and others are prevented from being damaged by interior parts of the eccentric oscillating gear mechanism or lubricant inside is prevented from leaking out.
A joint portion of the industrial robot described in JP-A-9-57678 is shown in FIG. 6. A joint portion of the industrial robot described in JP-A-2001-323972 is shown in FIG. 7. Note that like reference numerals are imparted to like or similar parts for description.
In JP-A-9-57678, a cylindrical tube body 330 is inserted into an eccentric oscillating gear mechanism 300 from an end plate portion 319a side thereof (from a lower side as viewed in FIG. 6), and a flange portion which is provided at one end portion of the cylindrical tube body 330 is fixed to the end plate portion 319a with bolts. The other end portion of the cylindrical tube body 330 is inserted into a turning part 360 of the robot, and an oil seal 341 is inserted between the turning part and the other end portion of the cylindrical tube body. This oil seal is intended to prevent the ingress of a lubricant residing within the eccentric oscillating gear mechanism into a hollow hole 331. In addition, oil seals 342, 343 are also inserted between an internal gear 303 and a carrier 319 in such a manner as to prevent the leakage of the lubricant to an outside of the gear mechanism.
In JP-A-2001-323972, a cylindrical tube body 330 is inserted from a fixing portion 350 side of the robot (from a lower side as viewed in FIG. 7), and a flange portion provided at one end portion of the cylindrical tube body 330 is fixed to the fixing portion with bolts. The other end portion of the cylindrical tube body is inserted into a turning part 360 of the robot, and an oil seal 341 is inserted between the turning part and the other end of the cylindrical tube body. This oil seal is intended to prevent the ingress of a lubricant residing within the eccentric oscillating gear mechanism into a hollow hole 331. In addition, an oil seal 343 is also inserted between an internal gear 303 and a carrier 319 in such a manner as to prevent the leakage of the lubricant to an outside of the gear mechanism.
In the eccentric oscillating gear mechanisms 300, 301 in JP-A-9-57678 and JP-A-2001-323972, respectively, the internal gear 303 is fixed to the fixing portion of the robot, and the carrier 319 is fixed to the turning part 360 of the robot. Output rotation of a motor 370 is reduced in speed by the eccentric oscillating gear mechanism and is then outputted to the carrier 319 as a reduced-speed rotation, whereby the turning part 360 of the robot rotates at low speeds.
In JP-A-9-57678, since the cylindrical tube body 330 is fixed to the end plate portion 319a, that is, the carrier 319, the cylindrical tube body 330 rotates together with the carrier 319. Although the cylindrical tube body 330 rotates at low speeds as has been described above, since cables and other members 380 are held to the fixing portion 350 by means of a fastening device 390, the cables and other members 380 are caused to rub against the rotating cylindrical tube body 330. Due to the rubbing contact of the cylindrical tube body 330 with the cables and other members 380 for a long period of time, there is caused a problem that the cables and other members are damaged.
On the other hand, in JP-A-2001-323972, since the cylindrical tube body 330 is fixed to the fixing portion 350 of the robot, the cylindrical tube body 330 does not rotate at all. Since the cylindrical tube body 330 does not rotate, there occurs no such situation that the cylindrical tube body 330 rubs against cables and other members which pass therethrough. However, to place the cylindrical tube body 330 into the fixing portion 350 of the robot in the way described above, the robot has to be lifted to be suspended by a crane or the like so that the cylindrical tube body is inserted into the fixing portion from therebelow and is then fixed thereto with bolts or the like, resulting in deteriorated working efficiency and safety. In addition, since the cylindrical tube body is mounted on the robot side, normally a robot manufacturer needs to prepare cylindrical tube bodies at their own load.